Resolve flake8 style warnings (mostly unused imports)

src/pretix/presale/views/__init__.py

@@ -1,4 +1,3 @@
-import uuid
 from itertools import groupby
 from datetime import timedelta
 from django.contrib.auth.views import redirect_to_login

src/pretix/presale/views/checkout.py

@@ -7,7 +7,7 @@ from django import forms
 from django.shortcuts import redirect
 from django.utils.functional import cached_property
 from django.utils.timezone import now
-from django.views.generic import View, TemplateView
+from django.views.generic import TemplateView
 from django.utils.translation import ugettext_lazy as _
 from pretix.base.models import CartPosition, Question, QuestionAnswer, Quota, Order, OrderPosition
 from pretix.base.signals import register_payment_providers

src/pretix/presale/views/order.py

@@ -19,7 +19,7 @@ class OrderDetailMixin:
                 user=self.request.user,
                 event=self.request.event,
                 code=self.kwargs['order'],
-                )
+            )
         except Order.DoesNotExist:
             return None